1. Field of the Invention
The present invention relates generally to the telecommunications field; and, more particularly, to miniature antenna apparatus for portable communications devices.
2. Description of the Prior Art
The use of portable communications devices, such as mobile telephones, has grown rapidly in recent years. Due to their increased usage and demand, mobile phones and the like have become smaller, lighter in weight and provide numerous features. Consumers, however, continue to demand even smaller and lighter devices that, at the same time, offer even more features.
An important component of mobile phones and other portable communications devices is the antenna used by the devices. In the case of small, lightweight devices, in particular, antennas are required that are also small in size. In addition, antennas that do not extend from the device, and, in fact, that are not even external to the device, are often considered highly desirable and are frequently touted in advertising campaigns in an effort to provide a manufacturer with a competitive edge in the marketplace.
Portable communications devices, such as mobile phones, that are currently in the marketplace utilize several different types of antennas. Among such antenna types include telescopic antennas, stub antennas and patch antennas. Telescopic and stub antennas are both external to the communications device and project outwardly from the chassis of the device. Patch antennas, on the other hand, may be incorporated within the chassis of the communications device; and for some users, communications devices with patch antennas are preferred over devices that include outwardly projecting antennas.
Portable communications devices operate in one or more of a plurality of frequency bands. Such bands include, for example, the 900 MHz, 1800 MHz and 1900 MHz bands (GSM and PCS bands). Accordingly, antennas designed for use in these devices must be able to operate in one or more of these frequency bands.
As the size of mobile phones and other portable communications devices is reduced, patch antennas for such devices must also be reduced in size in order to properly fit within the smaller devices. A reduction in the size of a patch antenna, however, often leads to certain undesirable characteristics with respect to the desired operating frequencies of the antenna. These undesirable characteristics may include, for example, a loss of efficiency, a reduction in bandwidth and a reduction in antenna gain.
There is, accordingly, a significant need for a patch antenna apparatus that is reduced in size so that it may be incorporated into the smaller mobile phones and other portable communications devices that are being developed; and, at the same time, that is capable of operating in a plurality of desired frequency bands while providing satisfactory performance in terms of efficiency, bandwidth and gain.
The present invention provides a patch antenna apparatus that is of small size so as to be able to fit within the chassis of a mobile phone or other portable communications devices, and that provides satisfactory performance characteristics when operating in desired frequency bands.
More particularly, one aspect of the present invention comprises an antenna apparatus for a portable communications device. The antenna apparatus comprises a patch radiator member, a ground-plane back-up element for the patch radiator member, and a feed arrangement connecting the patch radiator member to radio circuitry in the portable communications device. The patch radiator member includes an inner patch portion and an outer patch portion that are spaced from and substantially parallel to one another and that define a first open slot between first edges of the inner and outer patch portions. The patch radiator member also includes a metallic wall portion connecting second edges of the inner and outer patch portions that are opposed to the first edges. The metallic wall portion reflects a wave propagating toward the metallic wall portion and feeds the reflected wave toward the first open slot with a 180 degree phase reversal.
By providing the patch antenna apparatus according to the present invention, the apparatus can be significantly reduced in size; and, at the same time, provide satisfactory performance characteristics for use in a mobile phone or in other portable communications devices.
According to one embodiment of the invention, the inner patch portion is of an hourglass shape, and the outer patch portion is of rectangular shape. The hourglass shape of the inner patch portion makes it easier to transfer wave energy from a space between the inner patch portion of the patch radiator member and the ground-plane back-up element to the space between the inner and outer patch portions.
According to another embodiment of the invention, the ground-plane back-up element comprises a copper plate, and a copper strip connects a corner of the outer patch portion to the back side of the copper plate to lower the primary resonance frequency of the antenna apparatus.
According to a further embodiment of the invention, the antenna apparatus also includes a second open slot between the ground-plane back-up element and the second edge of the inner patch portion, and a third open slot between the ground-plane back-up element and the first edge of the inner patch portion. A wave emanating from the third open slot must also be phase-shifted by 180 degrees, and this is accomplished by including a reflector-and-slot extension metallic arm that extends from an end of the metallic wall portion parallel to one of the side edges of the patch portions, over the first edge of the inner patch portion and over the third open slot to provide the 180 degree phase shift by reflect-feedback of the outgoing wave from the third open slot.
According to yet further embodiments of the invention, an apparatus is provided that comprises a single patch portion and a reflector-and-slot extension metallic arm. The single patch portion can, for example, be of hourglass shape or of rectangular shape.
In general, the present invention provides a patch antenna apparatus that may be incorporated within the chassis of a mobile phone or other portable communications device. The antenna apparatus can be of small size, for example, 40 mm in width, 10 mm in depth and have a height of at least as small as about 19 mm, and still provide satisfactory operating characteristics at frequency bands of interest. The antenna apparatus can also be operated in either a broadband mode or a multiband mode by proper selection of the feedpoint of the feed arrangement and the ground point.